In the manufacture of garments from dyed cellulosic fabric, e.g., blue jeans from indigo-dyed denim, it is common to treat the denim so as to provide a "stone-washed" look (localized abrasion of the color in the denim surface). This can be achieved by agitating the denim in an aqueous medium containing a mechanical abrasion agent such as pumice, an abrading cellulase or a combination of these. It is preferred to run the process near neutral pH, so it is preferred to use a cellulase with high activity in this pH range. In the past, cellulase preparations were generally produced by cultivation of naturally occurring microorganisms, and such preparations invariably contained a mixture of many different cellulase components. A process using such a mixed cellulase preparation is described in U.S. Pat. No. 4,832,864 (to Ecolab).
The rapid advances in recombinant DNA techniques have made it possible to produce single-component enzymes in high yield, and processes using single-component cellulases have therefore become more interesting. Thus, WO 91/17243 and WO 95/09225 (Novo Nordisk) describe a process using a single-component endoglucanase denoted EG V with a molecular weight of .about.43 kD derived from Humicola insolens strain DSM 1800 with optimum activity near neutral pH. WO 94/21801 (Genencor) describes the use in "stone washing" of a single-component cellulase called EG III derived from Trichoderma longibrachiatum which is reported to have a pH optimum of 5.5-6.0 and to retain significant activity at alkaline pH. WO 95/16782 (Genencor International) suggests the use of other single-component cellulases derived from Trichoderma in "stone washing", but these cellulases are acidic and have virtually no activity at neutral pH.
A general problem in the known "stone washing" methods is that of back-staining, i.e. a phenomenon whereby dye already removed by abrasion deposits on parts of the fabric or garment so as to even out the desired variation of color density or to discolor any light-colored parts of the garment.